Water level at river mouth depends both on river discharges and wave conditions. At the state of
the art there is not a clear understanding of the role of wave set-up on the occurrence of this phenomena. There
are publications reporting field evidence that water levels at river mouth are not correlated to waves heights
whereas others field studies show exactly the opposite behavior. The correct interpretation of this phenomena
can be very useful in river mouth management. For instance, studying the hydraulic risk along a terminal part
of a river, numerical simulation of the free surface profile is usually employed. In such case the knowledge
of a realistic value for water level at river mouth is needed in order to define the down stream boundary
condition not highly conservative. In this work, the occurrence of wave set-up at an idealized river mouth due
to extreme wave condition in presence of wave-current interaction was studied. Any others causes influencing
the water level at river mouth was not considered. In fact this was achieved conducting the work by means of
numerical simulations. Moreover simulations were performed considering river mouth in shallow water condition
so that wave breaking occurs. Results agree with the field evidence that wave set-up is effective at river
mouth. Moreover, the effects arising from the wave-current interaction contribute significantly to its occurrence.

Water level at river mouth depends both on river discharges and wave conditions. At the state of
the art there is not a clear understanding of the role of wave set-up on the occurrence of this phenomena. There
are publications reporting field evidence that water levels at river mouth are not correlated to waves heights
whereas others field studies show exactly the opposite behavior. The correct interpretation of this phenomena
can be very useful in river mouth management. For instance, studying the hydraulic risk along a terminal part
of a river, numerical simulation of the free surface profile is usually employed. In such case the knowledge
of a realistic value for water level at river mouth is needed in order to define the down stream boundary
condition not highly conservative. In this work, the occurrence of wave set-up at an idealized river mouth due
to extreme wave condition in presence of wave-current interaction was studied. Any others causes influencing
the water level at river mouth was not considered. In fact this was achieved conducting the work by means of
numerical simulations. Moreover simulations were performed considering river mouth in shallow water condition
so that wave breaking occurs. Results agree with the field evidence that wave set-up is effective at river
mouth. Moreover, the effects arising from the wave-current interaction contribute significantly to its occurrence.